14 Mr. Bartlett's further Observations on the [Jan. 



to all times and places, proves to demonstration the 7/iiion of 

 miasmata with aqueous vapours; the former are heavy ; the latter, 

 possessing extreme le\ity and dilatibility, lend them wings. 

 Karified in the middle of the day by the heat, the more elastic and 

 lighter vapours must then occupy more space in the atmosphere; 

 the miasmata which they carry with them must also, at such 

 times, be more widely diftused ; we do not, therefore, inhale 

 them in such large doses in the same volume of air, and conse- 

 quently cannot ui those hours be so much affected by them. 

 M. Rigaud de I'lsle proves that miasmata are much less subtle 

 than the air, or the principle of smells ; since air and odorous 

 effluvia penetrate into every place, whereas miasmata are stop- 

 ped and expelled by various obstacles. " The interposition of a 

 forest, a mountain, a high wall, or even of a mere cloth, may also 

 co-operate in this separation, and preserve us in a variety ofcircum- 

 stancesfrom the pernicious effects of the air charged with deleterious 

 miasmata." 



The arguments of the non-contagionists have, 1 conceive, 

 been too ably refuted to require an additional exposition of their 

 fallacy. Were, however, further proofs necessary, the circum- 

 stances which attended the too early removal of the restrictions 

 upon the inhabitants of Marseilles, when the plague raged there 

 in 1720 ; and the fatal effects which followed the temerity of the 

 students of medicine at Edinburgh, some years since, during the 

 prevalence of the Infirmary fever, would sufhcienliy demonstrate 

 it. It is also, I think, equally clear that contagion c?.n be com- 

 municated by means of the respiratory organs only ; this opinion 

 experience hourly confirms. The Edmburgh Review for 

 March, 1819 (pp. 421, '122), with all its caution in giving an 

 opinion on questionable data, thinks it probable that conta- 

 gion " may be conveyed into tlie stomach by the sahva ; or it 

 may be absorbed by the skin in some instarwes ; but ice are 

 convinced that hi/ Jar the most ordinary way is inhalation by the 

 lungs.'' That the skin does not possess sufficient powers of 

 absorption, or the means of secreting pestilential viius, is proved 

 by the circumstance that all animal poisons (not excepting that 

 of snakes or the saliva of mad dogs), being innocuous, by mere 

 concact with the skin alone ; of course, I except those cutaneous 

 and other disorders which are nt t communicable by any other 

 means. Admitting, therefore, and it is not too much, that the 

 elements of contagion, as de ITsle proves, are disseminated in 

 conjunction with aqueous vapours, the efficacy of any measure 

 for its prevention must depend upon the resistance it opposes to 

 the passage of humidity. Now, how much soever the editor of 

 the Edinburgh Medical and Surgical Journal may question the 

 capability of gauze veils as preventives, Mr. Murray's communi- 

 cation (for wiiich I feel much indebted to that gentleman), in 

 your number for September, most satisfactorily demonstrates 

 that they actually will resist the passage of moisture. An expe- 



